damage has been done after a concussion exactly. but ucla researchers working with some former nfl players may have figured out the answer. our report from our chief medical editor, dr. nancy snyderman. >> reporter: wayne clark had his first major concussion as quarterback of the san diego chargers back in 1972. the doctors talked to him on the sidelines. clark didn't even remember his own name. >> i lost all recollection of that complete day before and after the concussion. >> reporter: but you didn't lose consciousness? >> right. >> reporter: you got clunked so hard on the head, you had amnesia. now 65, clark wonders about the long-term impact of his injuries. he's not the only one. we've all seen the headlines about chronic traumatic encephalopathy, or cte, a disorder that comes from repeated brain injury. up to now, can only be found after death as with star linebacker junior seau who committed suicide. doctors found the telltale abnormal clumps of protein in his brain. now researchers have developed a way to detect the damage early with a chemical that targets those proteins.